Central-energy telephone system.



P. W. DUNBAR. GENTRAL ENERGY TELEPHONE SYSTEM APPLICATION FILED MAR 22, 1901.

fill N IIIIIIIIIIIIIIIIWHIMIIIII R llllll In IIMIMI'II'I L m N "p java/2W, .mmw w QMMI/ Patented Feb. 21, 1911.

UNITED sTA EsraTEN'r OFFICE.

FRANCIS W. DUNIBA R, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

CENTRAL-ENERGY TELEPHONE SYSTEM.

To all whom it may concern:

Be it known that I, FRANCIS W. Duncan, citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Central-Energy Telephone Systems, of which thefollowing is a full, clear, concise, and exact description, reference bein had to the accompanying drawing, forming a part of this specification.

My invention relates to a central energy telephone system, my objectbeing to provide an improvement upon the telephone system disclosed in my Patent No. 686,272, dated Nov. 12th, 1901. In said patent I have shown the connection terminalnormally disconnected from the telephone line and adapted to be connected therewith, when connection is made with the line, through the agency of a relay. I have shown also a relay employed for the additional function of disconnecting the individual annunciator from the line when connection is made therewith. In my Reissue Patent No-.'12,031 dated September 1Qth,ltl02, I have shown means for energizing said relay by sending current over a portionot the talking circiut through the main contacts of the connection terminal and the connecting plug.v In said patent last above mentioned, I have illustrated a specific form of my invention wherein the winding of the relay is bridged between the limbs of the talking circuit, the relay being energized by a current from the charging source adapted.

to traverse a. metallic circuit including portions of the two talking limbs.

In accordance with the present invention, I provide means whereby the circuit for energizing the relay comprehends a portion of the talking circuit with return through a third conductor, as, for instance, the ground, common returnfor other suitable path, the present invention in this respect being a species under the generic invention disclosed in my patent last above mentioned.

Another feature of the present invention consists in the clearing out apparatus at the central station. I employ two relays one under the control of the subscribers switch and the other under the control of a switch at the central station, as, for instance, the operators plug, the two relays conjointly acting to control the lamp or other clearing Specification of Letters Patent. Application filed March 22, 1901.

Serial No. 52,315.

out signal. In the present invention I provide two separate relays adapted to conjointly control the circuit through the super visory signal, one of the relays serving When energized to open the circuit through the supervisory signal and the other serving when energized to close the said circuit. Accordingly, when the charging current traverses both relays the circuit of the signaling devicewill be open so that during conversation the supervisory signal remains unactuated. lVhen it is desired to actuate the supervisory signal, currentis sent through the relay which is adapted, when energized, to close the local circuit and the circuit of the other relay coil, is opened; in this manner the local circuit through the supervisory signal is closed and the supervisory signal is thereby actuated.

I have illustrated my invention in the accompanying drawing in which Figure 1 is a diag'am illustrating two subscribers lines and the central station apparatus for uniting the same for conversation. Fig. 2 is a similar diagram showing a modification in which the ringing currents are sent over metallic circuit.

Like letters refer to like parts in the scv- 4 terminate, respectively, in the springs, a", a", the spring, (i normally resting against contact, 1, and the spring, a, normally resting against Contact 2. Between the contacts, 1 and 2, are connected the individual annunciator or signal controlling relay, 0, and a battery, W, the springs, a", and a, carrying armatures adapted to be attracted by the relay magnet, b, one end of the winding of said relay magnet being grounded, while the opposite end is connected with contact, 5, and with the sleeves, (l (Z of the connection'terminals, d, d. The spring, a, when attracted, by the relay, is adapted to engage contact, 5, and likewise, the spring, 1/. is adapted to engage contact, 4, which iutltl' contact is connected with the line springs, 03, d.

At the substation are provided the usual microphone, 7, receiver,- f, and switch hook, it, normally resting against contact, 7, and adapted, when the receiver is removed,

Patented Feb. 21, 1911 currents, are encountered of sufficient magniwitha tip, 0, and a sleeve, 0 the former ceiver from the hook, thereby closing cir-' to en 'a e contact 8. Contact 7 is eon-I nected through bell, f and condenser, I, to ground. The condenser, i may be onntted if no extraneous currents, such as earth tude to interfere with the correct operation of relays h and is, as hereinafter described.

The telephone line B shown upon the right 5 of the drawing is provided with the same apparatus and circuits as line A, and like parts have been indicated by the same reference letters.

The answering plug, 77, is provided with a tip, p, and a sleeve, 20 the former being connected with strand, t, and the latter with strand, .9. The calling plug, 0, is provided being connected with-strand, if, and the latter with strand, 8''. The strands t, and t, are united through condenser, Z, and the strands, .5", and s, are united through a condenser, Z. Between the strands, t, and s, relays, 7L, and if, are provided, a battery, r, being interposed between said relays. Between the strands, t, and s, relays, is and are connected, a battery 7*, being interposed between said relays. The relay, h, controls spring, m normallyresting against contact, 14:, and adapted, when energized, to separate said contacts, in and 14. The relay, h controls spring, m, and is adapted, when energized, to move the same against contact 18. The relay contacts are connected in circuit with lamp,.m/ and battery, Relay in, controls contacts, '0 and 1t), and relay, k controls contacts, '0, and 15, and said contacts are included with the lamp 2:, in circuit with battery, 9".

The ringing key, g, normally engages contact, 9,.and is adapted to engage contact 10, connected through generator, g, to ground. The operators telephone set. 2', is adapted to be connectedbetwecn the strands, if, and s. and a condenser, I is connected in circuittherewith.

If subscriber A desires to converse with subscriber B, he removes his telephone recuit of battery, 11 through indicator, 0, over the limbs, (I, a, of the telephone line. The relay is thus actuated to convey to the operator the signal for connection. The operator lif'ts answering plug, 77, and inserts the, same in the connection terminal-belonging to line A, the circuitof battery, r, is thus closed from ground, over strand, a, sleeve, p sleeve. W, and through relay, 7), to ground. The relay is thereby actuated and attracts springs, a and a disconnecting the same from contacts, 1, and 2, respectively, and moving the same-into contact. respectively. with contacts, 4, and 5. The individual annunciator, c, is in this manner disconnected from the circuit, and the connection terminals are connected with the limbs of line A. Circuit of battery, I, is also elosedover strands, .5, fund limbs, (1 a of. substation A. The operater then con uects her telephone set, 2', in circuit, and learning that connection is desired with subscriber 13, she lifts calling plug, 0, and touches thetip thereof to the sleeve belonging to line B. If she hears a click in her telephone, she will know that line B is busy and that a connection is made therewith at another board. click she will know that the line is idle. If the line B is connected for conversation at another board, the sleeved will be connect- ,ed with a source of electricity and will thus be charged toa difference of potential rela tively to the earth or central office common return. Accordingly, when the tip of the -alling plug is touched to the sleeve, (Z currents will flow over the strand, 2 "and through the relay, Zr, to ground. The making and breaking of the circuit through the tip of the plug will cause a current of self' induction in the windings of relay, Z1, which will traverse the operators telephone set to produce the click in her telephone.

Assuming that the operator finds the-line" of subscriber B to be idle, she inserts the calling plug, 0, into the connection terminals belonging to line B.' The circuit of bat- If she hears no,

tery, 1"',.is thereby closed from ground over strand, .9, sleeve, 0 sleeve, (Z through relay, b, to ground. The relay is thus energized and connects the connection terminals of line B with the limbs of the telephone line. The o)erator then de Dresses rin in key, thereby sending current from generator, 9, through tip, 0, line spring, cl, contacts, 4 and (i and limb, a, through the bell of line, B, to ground. Since the ringing key, g, is inserted in the tip strand, and the tip strand alone is opened in ringing, the circuit of battery r, over the sleeve-strand and through the relay is not affected. Conse'quently, the sending of a ringing current does not interferewith the passage the current from battery, 1', through the relay of the called subscriber.

Duringconversation variationsof resistance caused by the microphone of subscriber A produce a corresponding variation of the difference of' potential between the points, a, and m", and correspondingly \-'arying currents are thereby caused to pass to substation B. Likewise, the microphone at the substation B varies the difference of poten-. tial between the points, y, and y, thereby,

propagating correspondingly varying currents which pass to substation A.

When the answering plug is lnserted in the connection terminal belonging to the call-mg subscriber, the circuit of battery, r,-

is closed through relays Zr, and 72 over strands, t, and s, and limbs, a, and a, Current is also closed from ground through battery, 1', relay, k strand, 8 and relay b, to ground. Both of the relays are thereb ergized and contacts, m, and 13, are closed togetherrwhile the contacts, m and 14 are separated. The circuit of battery, 1', through lamp, m, is thereby opened during conversation. Likewise, the insertion of the calling plug in the connection terminal of respective telephone receivers. Thus, Whensubscriber A hangs up his telephone 'receiver, the circuit of battery, 1', through relay, h, is opened, and the relay, h, is thus deenergized permitting contacts, m and 14 to close together. The circuit of battery, 1', remains closed through relay, it", its circuit being traced from ground through battery, 1 relay, k strand, 8, relay, 1;, to ground. Relay, 7L2, being thus energized, contacts, m,

and 13, are held together, and the circuit of battery, '1', is thus completed through lamp, m, thereby lighting the same, to convey 'to the operator the signal for disconnection. In a similar manner, the lamp, 0, is lighted when subscriber B hangs up his telephone receiver. Should either of the subscribers desire a reconnection Wit-h another party, he may, by vibrating his switch hook cause the intermittent lighting of the lamp belonging to his line to convey to the operator the signal for a new connection.

It will be noted that relays, it, and k, are under the control of the respective subscribers, while relays, 7e and A, are under the control ol the operator. Circuit is closed through relay, 11 by the inscrtion of answering plug. 7), and is opened by the withdrawal thereof; likewise. relay, k is under the control of calling plug, 0. Relay, I1, is

actuated by subscriber A through his switch hook and relay 7.1. by subscriber B through his switch hook. Each subscriber thus has two relays, oneunder the control of the operator and the other under the control of the subscriber and the lamp circuit is controlled by the conjoint action of the two relays.

In Fig. 2 I have illustrated a modification of my invention in which the calling currents are adapted to be sent over the metal -l'ic talking circuit; the circuit arrangements are similar to those shown in Fig. 1, except that the-bell. f, at the substation is adapted N to be br dged with a condenser Z, between.

the limbs. a, a, while the generator, gyat the central station is adapted to between the strands, t, and s.

y enbe bridged The contacts of the ringing key, associated with strands, 8', are adapted to ni'ziintain the con-' tinuity of the circuit of battery, 1", over the sleeve strand and through the relay, 1). When," therefore, the ringing key is depressed to bridge the generator, g, between the terminals of the callin plug, the circuit of battery, 1', from ground, through strand, 8, and through relay, Z), to ground is not interrupted.

It will be understood of course, that the indicators or annunciators may be replaced by any other form of signal controlling elec- 'tromagnets without departing from the spirit'of my invention. The telephone lines are freeirom constant grounds at the substations thus doing away with an objectionable feature of somesystems.

Having described my invention claim as new and desire to secure by Letters Patent is:

what I.

- 1. In a telephone system, the combination a with a telephone line, of a line signal therefor, a cord circuit, a magnet to render said signal inoperative during a connection, and a central source of current ada ted tofurnish current over the telephone line for talking purposes, said magnet being operated from said source during the connectionby current over a path including a portion of the cord and talking cn'cint and a third conductor, substantially as describedl 2. In a telephone system, the combination with a telephone line, of a line sigualtherefor, a cord circuit, an elec'tro-magnetic device actuated when a connection is established with the line to render said slgnal inoperative, and a central source of current' included in the metallic telephone line to furnish current for talking and for the op-' oration of said magnet, the actuating. wind ingot said magnet being connected during conversation between one side of the talking circuit and a third conductor and energized by current over a strand of the cord circuit, substantially as described.

3. In a telephone system, the combination with a telephone line, of a line signal. therefor at the central office, a magnet to render said signal inoperative when a connection is established with the line, a cord circuit to establish conversational circuits with the line, and a source ofcurrcnt associated with a established conversational circuit, .substantiallyas described.

4. In a telephone system, the combination with a telephone line, ofa line signal therefor at the central oilice, a magnet to render of talking current at the central stationsaid signal inoperative during connections, a cord circuit, and a source of current assoc1- ated with the line and cord circuit and" adapted to beincluded in the metallic line i during conversation, said magnet being actu ated by current from said source flowing over one side only ot the cord circuit with suitable return, said side of the cord circuit being included in the talking circuit, substantially as described.

5. The combination with a telephone line extending in two limbs to the central oflice, of a relay actuating winding adapted to be connected during a connection between one of said limbs and a third conductor, asource adapted to be connected during conversation between said third conductor and the limb with which said relay winding is connected and to send current through said relay winding over a circuit including a portion of the ta king circuit of the telephone line and cord circuit, substantially as described.

6. The combination witl1 a te'lepl1one line extending in two limbs to line contacts at the central station, of a relay actuating winding connected between one of said limbs and a third conductor, a cord connector terminating in connecting plugs, a charging source or electricity at the central station connected between said third conductor and one strand of the cord connector and adapted to be in cluded in the metallic circuit. of theline, and to send current through said relay winding over a circuit including one of the main ter minals of the connecting plug, a portion of the cord circuit, and a-line contact of the telephone line, substantially as described.

7. The combination-with a telephone line extending in two limbs t0 the central station,

of a line signal controlling electro-magnettherefor, a relay for rendering the line signal inoperative and having its winding connected during conversation between one of said limbs and a third conductor, a source of current at the central office adapted to be included in the metallic circuit of said line,

and means for closing circuit from said source through said relay winding over a portion of the talkmg c1rcu1t of the telephone line and cord circuit when connection is made with the line, substantially as described.

8. The combination with a telephone. line extending in two limbs to the central station,

ofiice adapted to be included in the metallic circuit of said line to furnish current to the substations for talking, and means for closi'ng clrcuit through said relay wind ng over a portion of the talking circuit when connection ismade with the line, substantially as described. I

9. The combination with a telephone line extending in two limbs to the central station, and having'line contacts thereat, of a,- |-relay actuating winding adapted to beconnee-ted between one of said limbsand a third conductor, a cord connector at the central station terminating in connecting plugs, a charging source of electricity adapted to be' bridged between the strands of said cord connector and having one pole connected with said third conductor and adapted to ,send current through said relay winding over a circuit including said thirdconductor anda portion of the talking circuit, substantially as described.

10. The combination with a telephone line and a connection terminaltherefor having two contacts each normally operatively disconnected from the line, of a third con ductor, a signal controlling electro-magnet normally connected with said line, a relay for disconnecting said-electro-magnet from the line, a cord circuit terminating in a con-' necting plug, a source of electricity connected with a: main terminal of the' plug, and -1neans for closing the circuit of said source through the winding of said relay when connection ismade with the line, said. relay winding circuit including said main termk nal of the connecting plug, and a line contact of the telephone line, with return through said third conductor, substantially as described.

11 The combination with a telephoneline and a connection terminal therefor, of 'a third conductor, a signal controlling electromagnet normally connected With the said line, a relayfor disconnecting said elect-rd. magnet from. the line, a cord circuit terminating in aconnecting plug, a'source of electricity adapted to .be bridged across the metallic circuit of the line for talking pur- I poses, and means for closing the circuit'of said source through the winding of said relay when connection is'made with the line, said relay winding circuit including a talk ing strand of the cord circuit, a main terminal of the connectingplug, a linecontac't and a portion of a talking limb of thetelee phone line, with return through said third conductor, substantially as described.

12. In a telephone system, the combina tion with a multiple switchboard telephone line, of a line signal therefor, a cord circuit, an electro-magnet actuated when a connection is established with the. line for conversational purposes to render said signal inoperative, a central source of current included in the metallic line to furnish current-for talking and for the operation of said magnet, the actuating winding of said magnet .being connected during .conversw tion between one side of the talking circuit and by means of an extra conductor with one pole of said source, the circuit of said actuating winding including a. part of the cord circuit, substantially as described.

'13. In a telephone system, the combination with a multiple switchboard telephone line, of a line signal therefor, a cord circuit, an electro-magnet actuated when a connection is established with the line for conversational purposes to render said signal inoperative, a central source of current included in the metallic line to furnish current for talking and for the operation of said magnet, the actuating winding of said'niagnet being connected on one side to the telephone line and on the other side to an auxiliary -conductor leading to one pole of said source, the circuit ol 'said actuating winding including a part of the cord circuit, substantially as described.

14; In a telephone system, the combina-' tion with a multiple switchboard telephone line, of a,l1ne signal therefor, a cord circuit, an electro-magnet actuated when a contion with a-multiple switchboard telephone line, of a line signal therefor. a cord circuit, an electro-magnet actuated when a connection is established with the line for conversational purposes to render said signal inoperative, a central source of current included in the metallic line to furnish current for talking and for the operation of said magnet, the actuating winding of said magnet being connected during conversation directly between one side of the talking circuit and one pole of said source outside the 'tal kin'g circuit. the other pole of said source being connected with one side of the talking and cord circuit, substantially as described.

16. In a telephone system. the combination with a multiple switchboard telephone line, of a line signal therefor, a cord circuit, an -electro-magnet actuated when a connection is established with the line for .conver sational purposes to render said signal inoperative, a central source'of current included 'in the metallic line to furnish current for talking and for the operation of said magnet.-the actuating winding ofsaid. magnet under certain conditions of use being mcluded in a local circuit with said source of current and including a portion of one side only of the talking circuit and a part of the cord circuit, substantially as described.

17. In atelephone system, the combination with a multiple s\\'itchboar(l telephone line, or. a. line signal therefor, a cord circuit, an electromagnet actuated when a connection is established with the line for conversational purposes to render said signal inoperative, a 'metallic line circuit including said line established upon said connection, a central source of current included in the metal lic line to furnish current for talking and for the operation of said magnet, the actuating winding of said magnet being connected during conversation on one side with one side of the metallic line and on the other side bymeans of an auxiliary conductor with-one pole of said source, the other pole of said source being connected with one side of the cord circuit to send current through said actuating winding over a part of the cord circuit, substantially as described.

l 8. The combination with a telephone line extending in two limbs to the central station, of a relay actuating winding adapted to be connected between one of said limbs and a third conductor, a cord circuit, a charging source of electricity at the central station adapted to be connected between the third conductor and said limb through the mediumof the cord circuit to send current through said relay winding, said source also being connected in the metallic circuit to furnish current for talking purposes, a calling generator at the central station, and means for sending calling current therefrom over the line of the called subscriber only, and at the same time maintaining said relay in, operated condition, substantially as described.

' 1 9. The combination with a telephone line extending in two limbs to the central sta-.

tion, of a relay actuating winding adapted to be connected between one of said limbs and a third conductor. a cord circuit, acharging source of electricity at the central sta. tion adapted to be connected by means of the cord circuit between the third conductor and said limb to send current through said relay winding. said source als being connected in the metallic circuit to furnish current for talking purposes. a calling generator at the central station. and means for sending calling current therefrom over the line of the called subscriber only and at the same timemaintaining said relay operated from said charging source, substantially as described.

20. The combination with a telephone line. extending in two limbs to the central slat ion. of a relay actuating winding adapted to be connected between one of said limbs and a third conductor, a cord circuit. a charging source of electricity at the central station adapted to be connected by the cord circuit between the third conductor and said limb to send current through said relay winding, said source also being connected in themetallic circuit to furnish current for talking purposes, a calling generator at the central station, a ringing key for connecting said calling generator with the line of the called subscriber-and for opening one of the limbs of the line, whereby the calling current reaches the called subscriber only and the said relay is maintained operated during calling. substantially as described.

21. The combination with a telephone line extending in two limbs to the central station, of a relay actuating windingadapted to be connected between one of said limbs and a third conductor, a cordcircuit, a charging source' of electricity at the central station adapted to be connected by means of the cord circuit between the third conductor and said limb to send current through said relay winding, said source also being connected in the metallic circuit to furnish current for talking purposes, a calling generator at the central station, a ringing key for connecting said calling generator with the line of the called subscriber and ior opening the second limb of the line, whereby the calling current reaches the called subscriber alone andthe said relay is maintained operated during calling, substantially as described. 22. The combination with a telephone line extending in two limbs to the central station,

of arelay actuating winding adapted to be- .connectedbctween one of said limbs and a third conductor. a cord circuit, a charging source of electricity at the central station adapted to be connected between'the third conductor and said limb through the medium of the cord circuit tosend current through said relay winding, said source also being connected in the metallic circuit to furnish current for talking purposes, a calling generator at the central station, a ringing key for connecting said calling generator with the line of the called subscriber and for opening the second limb of said line, the first limb remainingclosed during said operation of the ringing key, whereby a calling current is prevented from reaching the calling subscriber and the relay is'maintained operated during calling, substantially as described.

23. The combination witha telephone line extending intwo limbs l0.lll central station, of a relay actuating winding adapted to be connected between one of said limbs and a Third conductor, a cord circuit, a charging source of electricity at the central station adapted to be connected between the third conductor and said limb by means of the k'ul'tl circu t to send current through said re;-

lay winding, Saidrource also being connect ed in the metallic circuit to furnish current for talking purposes, a." calling generator at the central station, and'means for sending calling current therefrom over the other limb of the telephone 'line' with suitable return, substantially as described.

The combination'with a telephone line extending in two limbs to the central station,

of a relay actuating winding adapted to be connected. between one of said limbs and-a third conductor, a charging source of electricity adapted to be bridged between the two limbs at the central station and having one pole connected with'said third conductor and adapted to sendcurrent through said relay winding, a hell or signaling device-at the substation connected between, the opposite limb of the telephone line and the third conductor, a calling generator at the central station, and a ringing key for connecting said calling generator with said opposite limb and for disconnecting said charging source from said opposite limb, substantially as described. 7

25. In a telephone system, the combination with a telephone line, a source of cur- .rent to furnish current for talking. a cord circuit, a line .signal tor the line, an clectro-.

magnetic device to render the signal inoperatlve during a connection and operated by current from said source over a portion of' the cord and talking circuit, and means for sending a non-continuous ringing current out over the called line only and without interrupting the flow of continuous current from said source through said device, substantially as described.

2a. In atelephone system, the combination with .a telephone line, a source of current to furnishcurrent for talking, a cord circuit, a line signal for the line, an electromagnet to render the signal inoperative d'ur mg a connection and actuated by current from said source over a portion or" the cord and talking circuit, and means for sending anon-continuous ringing current out over the called line only and without interrupting the path of current from said source through .said electro-inaghet, substantially asdescribed. i g

27. The combination with a telephone line, of a line signal therefor, an electromagnet adapted to render said signal inoperative during a connection, a cord circuit, a source of current connected with the line to furnish current to the substation for talking purposes and for the operation of said electro-magnet. the circuit through said electro-magnet having a portion coincident with the cord and talking. circuit, and

means for maintaining said el-ectro-magnet actuated from said talking source during the time the. wanted subscriber is being called, substantially as described.

28. The combination with; a. telephone of current connected with the line to furnish current to the substation for talking purposes and for the operation'of said magnet, the circuit, through said magnet being completed over a portion ofthe cord and talking circuit, and means for maintaining said magnet actuated by current from said source and for simultaneously sending a non-continuous. ringing current out over the called line to call the subscriber, substantially as described. 7

29. The combinationwith a telephone line, of a line signal therefor, a magnet adapted to render said signal inoperative during a connection, a cord circuit, a source of current connected with the line to furnish current to the'substation for talking purposes and for the operation of said magnet, the circuit of said magnet being completed over a portion of the cord and talking circuit, and means for maintaining said magnet actuated by current from said source and for simultaneously sending anon-continuous ringing current out over the called line only to callthe subscriber, described.

30, The combination witha telephone line. of a line signal therefor, a magnet to render said signal inoperative during connections, acord connector for uniting said substantially as 'line with another telephone line, a source of continuous current adapted to be connected with said cord connector to send current through said magnet and over the telephone line for talking purposes, a calling generator adapted to produce a non-continuous current, a ringing key adapted to-conn'ect said calling generator with the line and without disconnecting said source wlnle the calling generator is in circuit, whereby said magnet is energized from said source while the subscriber is being called, substantially as described. v

31. The combination with a telephone line, of a connection terminal normally disconnected therefrom, a signal for the line, a magnet for connecting said connection terminal with the line and for rendering said signal inoperative, a source of continuous current connected in the line to furnish current for talking purposes and adapted to energize said magnet over a circuit having a portion coincident with the talking circuit, a calling generator, a ringing key adapted to connect said calling generator with the line, and means for maintaining said magnet energized from said source during the time the calling generator is connectedin circuit, substantially as described.

The combination. with a telephone line,'of a connection terminal normally in inoperative relation with the line, a signal inoperative relation therewith, a magnet for placing said connection terminal in operative relation with. the line and for rendering said signal inoperative, a source of continuous current adapted to energize said magnet over a circuit including a portion ofthe talking circuit and to also furnish current over the line for talking purposes, a ringing key adapted to connect said calling generator with the line and to open the metallic circuit to the calling telephone line whereby-a calling subscriber is not disturbed, and means for energizing said magnet from said source during the time the calling generator is in circuit, substantially as described.

33. In a telephone system, the combination with a telephone line, of a line signal therefor, a magnet to render said signal inoperative during a connection, a cord circuit, a steady current source to furnish current for talking and for operating said magnet over a portion of the cord and talking circuit, a ringing generator adapted to be connected with the line to call the wanted subscriber, the current from said source serving to maintain said magnet operated during ringing, substantially as described.

34. The combination with a telephone line, of a connection terminal normally disconnected therefrom, a magnet for connecting said connection terminal with the line during connections, a central source of current adapted to be connected 1n the metallic circuit for talking purposes, means for operating said magnet from said source when connection is made with the line by current flowing over a path including a portion of the talking circuit, and means for sending a calling current over the line of the called subscriber only and at the same time maintaining said magnet in operative condition by current from said source, substantially asdescribed.

The combination with a telephone line, of a connection terminal normally disconnected therefrom. a magnet for connecting sald connection terminal with the line, a source of continuous current adapted to be included in the metallic line for conversation,

-a calling generator, said talking source being adapted to energize'said relay over the talking circuit when connection is made with the line, aringing key for connecting said calling source with the line of 11 called subscriber without disconnecting said continuous current source, whereby said magnet is energized from said source during the time the calling generator is connected with the line, substantially as described.

36. In a telephone system, the combination with a telephone line, of a source of current and a relay bridged between the two limbs of the talking circuit thereof at the central ofiice, a. second relay in a local circuit at the central station, said local circuit having a po-rtlon co1nc1dent with the talking circuit, and a signal controlled by the QOIIJOl-Dt action of said relays, substantially as described.

37. In atelephone system, the combination with a telephone line, of a charging source of electricity and a relay connected with the tip trand of the cord circuit whereby the same is adapted to be operated over the telephone line, a second relay at the central ofiice connected with the s'leeye and talking strand of the plug circuit and adapted to be closed in a local circuit during conversation, where'- with a telephone line,-a line signal, a cut-'ofi relay to render the signal inoperatlve, a cord by the same is operated as long as the plug is in the jack, and a signal in a local circuit including the contacts of both said relays,

circuit and source of current associated with the line, 0f a supervisory signal associated with said cord circuit, and means for establishing a path for current over one side of the talking circuit of said. cord circuit to operate said 'cut-ofl' relay and said supervisory signal, and a relay adapted to render the said signal inoperative and having its winding in a path for current over the other side of said cord circuit and telephone line,

said relay being controlled byvthe subscriben substantially as described.

40. In atelephone system, the combination with a telephone line and cord circuit adapted to connect with said line, of a supervisory signal associated with said cord circuit and adapted to be operated by current in a .local circuit including one side of said cord andtalking circuit when connected with the line, and means controlled by the subscriber for rendering said signal inoperative by current passed over the line circuit; substantially as described. 1

41. In a telephone system, the combination with a. telephone line and cord circuit adapted to connect with said line, of a supervisory signal associated with said'cord Cir-f cuit and adapted to be operated when a connection exists by current passed over oneside -01 said cord and talking circuit and over asuitable office return and not under the control of the subscriber, and means under the control of the subscriber'for rendering said signalinoperative by current passed over the 'linecircuit, substantially as described.

42. In a telephone system, thecombiuatiou with a'telephone line, a cut-off relay and cord circuit adapted to connect with said line, of a supervisory signal associated with Said cord circuit and adapted when a connection exists to be operated over a local circuit having a part co-incidentwith the talking circuit and not under the control of the subscriber, said local circuit including .ing of the cutoff relay being included in the path of said current whereby it is operated, and means controlled by the subscriber for rendering said signal inoperative by current passing over 'the line circuit, substantially as described. i

44. In a telephone system, thecoinbination with a telephone line and cut-oii relay therefor, of, acord circuit adapted to connect with said line. of a supervisory signal associated with said line circuit and adapted tobe op erated when a connection exist-s by current passing over one side of said cord and talki'ng circuit and over a suitable ofiice return and not .under the control of the subscriber, the'aetuating winding of said cut-ofi relay being also included in the path of said current, and means under the control of the subscriber for renderingsaid signal inoperativeby current passing over the line circuit. substantially as described p 45..'In a telephone system, the combination with a subscribers telephone and line circuit normally discontinuous or open to direct currents at the subscribers station, of a main line terminal consisting of two normally open contact pieces at the central oifice, a cord circuit consisting of two strands and with contact terminals adapted to connect with the contact terminals of the line when the line is connected for conversation, a source of current associated with said cord circuit and adapted to send current over the telephone line to feed the subscribers trans.- mitter, a supervisory signal associated with said cord circuit and adapted to be placed in condition to operate over one side of said cord circuit when connected with the line,

the circuit for operating said signal being 'completed over a local circult at the central ofiice. and means under the control of the station to form a path for current over the line circuit, substantially as described.

46. In a telephone system, the combma tion with a main line normally open or discontinuous at the subscribers station, of a telephone instrument' at said subscribers station, a calling signal normally associated with the line at the central office, a cut-off relay at the central ofiice adapted to render the calling signal inoperative when connection is made with the line, a line terminal for the said line, a cord circuit consisting of two conductors each forming a part of the talking circuit and adapted to be placed in connection with the said line terminal, a source of current associated with said cord circuit and adapted to send current over the line circuit for energizing the subscribers transmitter (luring conversation. a supervisory signal associated with said cord circuit and adapted to be placed in condition to operate when connection is made with said line over a local circuit includii'ig-the cut-oft rclay or electro-magnet. said circuit not including the subscril ie1"s instrument, and means controlled by the subscriber t'or rendering the said supervisory signal inoperative by current from the said source-located in the cord circuit and sent over the line. substantially as described.

it". The combination with a telephoneline, ot' a subscribers station, a line terminal at the central oflice associated with said line, a cord circuit consisting of two conductors forming a part of each side of the talking circuit and adapted tobe united to the said line circuit by means-of registering contacts in the line terin'inaland cord terminal, a source of current and a supervisory signal associated with said cord circuit and adapted to be operated when connection is made with the line by means of an electro-magnet operated over a circuit established by the connection of the cord circuit with the line circuit, said circuit being local and not completed through the subscribers instrument, and means under the control of the subscriber for rendering inoperative the said signal'by current passed over the line circuit. substantially as described.

48. In a telephone system,.the combination with a line circuit, of a subscribers telephone, a line terminal at the central of: fiee consisting of two contacts registering with two contacts in a cord circuitwhen connection is made with the line, said cord circuit including a source 'of'current for.

energizing the Subscribers transmitter, a

, supervisory signal associated with said cord circuit and adapted to'be placed in condition to operate by current over one side of the cord and talking circuit when connection is made with the line, said circuit being local and not underthe control of the subscriber. and means for rendering the said signal inoperative by current sent over the main line. said flow of current being under the control of the subscriber, substantially as described. i

.49. In a telephone system, the combination with a subscriber's instrument, of.a line circuit, a calling signal and a cut-off re'la y. said relay being adapted to render the line signal inoperative when a connection is made with the line. a connection terminal for said line at the central oflice consisting of two contacts adapted to register with the two contacts of a cord circuit, said cord circuit including a source of current adapted to supply current for energizing the subscriber's transmitter. a supervisory signal associated with said cord circuit, said signal being placed in condition to operate when connection is made with a-line and the subscriber's instrument is not in use by current flowing over one side of the talking circuit and in a circuit local to the exchange, said local circuit including an operative winding of the cut-off relay, means con trolled by the removal of the subscribers instrument from its hook for rendering said supervisory signal inoperative by current sent over the main line from said source, and further means for maintaining the cutoff relay operated while connection is made with the line. substantially as described.

50. In a telephone exchange system. the combination with a subscriber's telephone line. of a cutoff relay therefor, a cord circuit. a pair of magnetic windings and a source of current in bridge of the talking strands of said cord circuit. one of said windings and said cutoff relay being energized by current from said source over a portion of a talking strand of said cord circuit upon connection between said line and cord circuit, a supervisory signal for said cord displayed responsive to said energization of said winding and means under control of the subscriber to include the other winding and the line limbs in circuit with said source and first said windings whereby said other winding is energized to efi'ace said signal.

51. In a telephone exchange system. the combination with a subscribers telephone line of. a cutoff relay therefor, a cord circuit. a pair of magnetic windings and a source of current in bridge of the talking strands of said cord circuit, a supervisory signal for said cord circuit, said cutoff relay and one of said windings being energized over av portion of one of the talking strands of the cord circuit, responsive to a connection between said line and cord circuit, whereby said signal is'displayed, and means under.

the control of the subscriber to include said telephone line and the other winding in circuit with the first saidwindiug whereby control of the subscriber to include the lat- I ter'winding in circuit with the first said winding to render the latter winding effective. v

In a telephone" exchange system the combination with a subscribervs telephone line of a cutoff relay therefor, a cord circuit, a pair of magnetic windings and a source of current in bridge of the talking conductors of said cord, one of said windings ,and said cutoff relay being rendered effective by current from'said source over a portion of one of the talking conductors of the cord, and means controlled by the subscriber to include the other winding and the telephone line in series with the first said winding and said source, whereby the said second winding is rendered effective.

In a telephone exchange system, the combination with a telephone line, of a cutoff relay therefor, a cord circuit, a signal for said cord, a source of current and a pair of magnetic windings in bridge of the talking conductors of said cord, a circuit connection for said relay and one of said windings, established over a portion of a talking strand of the cord responsive to connection between said line and cord, whereby said winding isrcndercd elfectix'e to display said vsignal. and a switch at the sub-station of said line operated to alter the circuit of said.

windings, whereby said second winding is rendered effective to efface said signal.

'55. In a telephone exchange system. the combination of a telephone line, a cutoff relay therefor, a cord circuit, a signal for said cord circuit, a magnetic winding for controlling said signal, a sourceof current and a circuit connection closed during the connection of said cord circuit to said line whereby said cutoff relay and said winding are energized by current from said source over a portion of one of the talking strands of said cord circuit.

56. In a telephone exchange system, the combination of a line extending in two limbs to a sub-station, a cutoff relay therefor, a

cord circuit, a signal for said cord circuit,

oil relay and one of said windings are en-- ergizcd, by current from said source over a portion of one of the talking strands of said cord circuit, and a switch at the substation forclosing a circuit of said source including the two limbs of said line and both of said windings. v

57. In a telephone exchange system, the con'ibination with a sub-station telephone line. of cutofi relay therefor, a cord circuit, a signal for said cord. a magnetic winding for controlling said signal, a source of talking current, a circuit connection, closed during a connection of said cord to said line whereby said cutoff relay and said winding are energized by current from said source over a portion of a talking strand of said cord circuit, a transmitter atsaid sub-station, and a switch at said sub-station adapted to connect said transmitter in circuit with said winding and said source to supply talking current to said transmitter through said winding.

58. In atelephone exchange system, the combination of a telephone line extending in two limbs to a sub-station. a cutoff relay therefor, a cord circuit, a signal for said cord circuit, two magnetic windings for controlling said signal, a source of talking current, a circuit connection closed during the connection of said cord circuit to said line whereby said cutoff relay and one of said windings are energized by current from said source over a portion of one of the talking strands of said cord circuit, a switch at the sub-station for closing a circuit of said source including the two limbs of said line and both of said windings, and a transmitter at said substation adapted to be included in, the latter circuit, the talking current for said transmitter being supplied from said source over said windii'igs and said line limbs.

In witness whereof, I have hereunto sill)- scribed my name in the presence of two witnesses.

FRANCIS VT. DUNBAIL .lVitnesses:

JosarH' C. BELDEN, MELANoTnoN R. NrMAN. 

